In the fields of optics, precision machines, building materials, home electronics and so forth, lamination of a film having an antistatic ability is supposed to be useful for the purpose of preventing dust attachment, electric circuit failure and the like. Above all, in the field of home electronics, from the standpoint of preventing dusts or avoiding a failure during panel fabrication, an antistatic property is required of the protective film applied to an image display device such as a cathode ray tube (CRT), plasma display panel (PDP), electroluminescent display (ELD) and liquid crystal display (LCD).
In addition to the antistatic property, various functions such as glare prevention, antireflection, hardcoat performance and antifouling property are sometimes required of the protective film of the above-described image display device, and it is important to satisfy these functions all at the same time.
As for the method to impart an antistatic performance to an optical film used in an image display device, an antireflection film having a layer where electrically conductive inorganic metal oxide particles are dispersed in an organic binder has been conventionally known (see, JP-A-2005-196122 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)). However, the refractive index of an electrically conductive particle conventionally used in general is as high as approximately from 1.6 to 2.2 and therefore, when an inorganic metal oxide particle is used in an optical film, the refractive index of the layer containing such a particle is increased. The increase in the refractive index of the layer may allow for occurrence of unintended interference fringe due to a difference in the refractive index from an adjacent layer or may cause a problem such as intensified tint of the reflected color.
On the other hand, an electrically conductive polymer is known as an electrically conductive material replacing the inorganic oxide particle. For example, a polythiophene containing a polyanion has been developed as the electrically conductive polymer, and a technique of forming an electrically conductive film using the polymer is disclosed (European Patent No. 440,957). This electrically conductive film is not high in the refractive index as compared with an inorganic fine particle-containing antistatic film, but because the film is formed of an electrically conductive polymer alone, the strength of the coat is weak and its application as a protective film has a problem.
To cope with this problem, a coating film composed of an electrically conductive polymer and a curable binder is disclosed (JP-A-2004-91618 and JP-A-2006-176681). However, such a technique is disadvantageous in that the durability such as light resistance, heat resistance and wet heat resistance, particularly light resistance, is poor and the electrical conductivity is significantly impaired due to light irradiation.
Meanwhile, for enhancing the wet heat resistance, it has been proposed to use an electrically conductive polymer in which a hydroxy group-containing aromatic compound having two or more hydroxyl groups bonded to the aromatic ring is mixed (JP-A-2006-131873).